Refrigeration



C. c. COONS nmlm'rron Aug. 28, 1951 2 SheetsSheet 2 Filed April 2. 1.947

INVENTOR.

fsa'

cada., c. come y,

` ATTORNEY.

l' Patented Aug. 28,V 1951 2,566,170 I asraroaaa'rlos CurtisC. Coons, North Canton, Ohio, assignor to The Hoover Company, North Canton, Ohio, a

'corporation of Ohio Application April 2, 1947, Serial No. 738,874

(ci. cs2- 5) l 12 Claims. l

The present invention relates to the art of refrigeration and more particularly to refrigerating apparatus of the intermittent absorption type.

It is a principal object of the present invention to provide a dual intermittent absorption refrigerating apparatus in which, other conditions being equal, the evaporator temperatures are maintained more uniform and at lowerlevels than heretofore possible.

It is a further object of the present invention to provide an intermittent absorption refrigerating apparatus providedwith two evaporators in which one evaporator is so arranged that it is vapor locked and inactive until the other evaporator has evaporated a major portion of the liquid refrigerant supplied to the evaporating asi sembly.

It is a further object of the present invention to provide a dual intermittent absorption refrigerating apparatus which is so constructed and arranged that liquid refrigerant remaining in the evaporating system of each refrigerating unit at the end of an evaporating period thereof is conveyed in heat transfer relationship with the liquid receiver of the associated unit to pre-cool theliquid refrigerant about to engage in the evaporating process in the associated unit.

Other objects and advantages of the invention will become apparent as the description proceeds when taken in connection with the accompanying drawing in which Figure 1 is a schematic representation of a dual intermittent absorption refrigeratlng apparatus embodying the invention. Figure 2 is a perspective view of the evaporating assembly of the apparatus illustrated in Figure l. Figure 3 is a partial sectional elevational view showing the manner in which the evaporator of Figure 2 is assembled with a cabinet construction. Figure 4 is a partial sectional view .of the evaporator structure illustrating certain liquid level conditions in relation to the parts.

It is characteristic of the intermittent absorption type refrigerating apparatus that the evaporator y temperature approaches the condensation temperature of the refrigerating medium as determined by the cooling medium for the sys- Y tem at the beginning of any period of refrigeration production. As the generator-absorber of the apparatus is cooled, evaporation of refrigerant in the evaporator quickly lowers the temperature of the evaporator and its content to a low value which is substantially maintained until approximately 10 to 15 percent of the total refrigerant charge system remains in the liquid state in the evaporator. At this point in the op- 2 eration of the system, the progressive enrichment of the absorbent, whether it be liquid or solid material, tends to'slow the evaporating process to such an extent that the evaporation occurs at progressively higher temperatures and pressures. Such an increase in temperature is generally continued until the evaporator temperature has increased above the freezing pointbefore the absorbing period of the apparatus is completed. Furthermore the period ottime required to remove the aforesaid remnant of refrigerant liquid in the evaporator may account for as much as 30 or 40 percent of the total time consumed during the absorbing period of the apparatus. This is a time period during which the eifective refrigeration produced is comparatively insignificant when comparedwith the useful refrigeration produced during the initial stages of the evaporating period.

In accordance with the present invention however, the total length of the absorbing period is greatly shortened by conducting the aforesaid remnant of refrigerant liquid into heat exchange with the comparatively high temperature liquid receiver of the associated system. This produces considerably higher pressures in the absorbing system and higher temperature evaporation of this liquid which is much more readily absorbed in a short period of time by the partially saturated absorbent. A double gain results from this j in that the total length of the absorbing period is materially shortened without significantly shortening the useful refrigeration producing extent thereof while at the same time the aforesaid remnant of liquid refrigerant is evaporated at comparatively vhigh temperatures and pressures in a manner in which it takes up a refrigerating load which is normally thrust upon liquid refrigerant in the system which could otherwise evaporate at greatly lower temperatures.

Referring now to the drawing in detail and first of Figure 1 thereof, there is illustrated a dual intermittent absorption refrigerating system of the dry salt type. VSince the two systems are identical with each other only one will be described in detail. Corresponding identical parts of the two systems are given the same reference characters with the parts of the right hand system as viewed in Figure 1 distinguished by a prime. l

4The refrigerating system proper comprises a generator-absorber A which may contain either a liquid absorbent such as water or a solid absorbent such as strontium chloride. Refrigerant vapor such as ammonia produced in the generato an air cooled condenser C wherein it is reduced to the liquid state and discharged through a conduit I2 into an evaporator assembly E.

Heat is applied to the generator-absorber A in any suitable manner as by gaseous fuel burner I4 which discharges products of combustion into a flue I5 extending centrally through the generator-absorbcr A. Fuel is supplied to the burner I4 through a gas supplying conduit IB, a safety pilot cut-off arrangement I1, and solenoid valve I8, which is interposed in the gas conduit I9. The burner I4 is ignited from the safety pilot I'I by a flash tube 2l).

A cooling fluid jacket 22 extends centrally through the generator-absorber around the products of combustion flue I5 and communicates with a conduit 23 which leads to a secondary condenser 24. The secondary cooling medium may be any desired volatile substance such as methyl chloride. condensate formed in the secondary condenser-s 24 and 24 discharges into a secondary receiver 25 and is conveyed therefrom through a conduit 26 to a chamber 21 which houses a snap acting cooling medium flow control valve 28. The valve 23 is so arranged that it has two positions. In the position shown, cooling medium may ilow through the conduit 29' to the cooling jacket 22 of absorber A whereas flow through the conduit 29 to the generatorabsorber A is prevented. In its other position, the flow of cooling medium is reversed with respect to the chamber 21.

The snap acting valve 28 includes an actuating arm 30 which is positioned between the opposed operating ends of thermostats 3I-3I which are responsive to the temperatures of generatorabsorbers A and A', respectively.

The solenoid valves I8--I8' are each connected to line wire 33 and are each also connected by conductors 34-34, respectively, to a two position snap acting switch element 35. Switch 35 is arranged to connect conductor 34 or 34' to the other line wire 36 depending upon which of its two positions it assumes. The snap acting switch 35 has an operating lever 38 positioned in the path of movement of the actuating arm 30 so as to be operated simultaneously with the snap acting valve 28.

The operation of`the control mechanism is as follows: In the position shown in Figure 1, the generator-absorber A has just commenced a heating period of operation. As the temperature of -the generator-absorber A progressively increases, a temperature is reached at which the thermostat 3| operates the lever 33 over center. When lever 3U snaps over center the valve 28 snaps to its opposite position to allow ow of cooling medium to generator-absorber A and to discontinue ilow of cooling medium to generator-absorber A'. Simultaneously with the foregoing the lever 30 operates the switch 35 to de-energize solenoid valve I8 and to energize solenoid valve I8 to supply heat to generatorabsorber A'.

The foregoing provides the manner in which the two intermittent absorption refrigerating apparatuses are alternately heated and cooled in out-of-phase relation with each other. By this arrangement a substantially continuous production of refrigerating effect is achieved as the evaporator E or evaporator E' is always charged with liquid and open to a generator-absorber which is being cooled to induce evaporation of refrigerant and hence the production of a useful refrigerating eil'ect.

Referring now to Figures 2 to 4 in particular, the evaporator assembly comprises a. liquid receiver 40 to which is connected the principal chilling element 4I by a liquid inlet pipe 42. The chilling element 4| as illustrated is divided into two parts one of' which is adapted to be positioned within and one without an ice freezing housing or chamber 45, shown in dotted outline in Figure l, and in Figure 3. The section 4I of the evaporator is provided with vapor discharge .conduits 43 opening into the upper portion of the liquid receiver 40 above the maximum liquid level normally encountered therein. As shown more clearly in Figure 4, the liquid receivers 40-40 are inclined downwardly slightly toward each other for a purpose to be-developed hereinafter. The maximum liquid level which will be created in the liquid receiver 4I! is indicated by a dotted line 44 which is below the level of the vapor pipe 43. While it is desirable that the vapor pipe 43 be free and above the maximum liquid level in the apparatus this last is not essential so long as this evaporator is arranged so that vapor formed therein always has a free untrapped path through liquid to the conduit returning vapor to the generator-absorber.

The liquid inlet conduit 42 for the evaporator.

element 4I opens into the liquid receiver 40 at appreciable distance above the bottom thereof. The elevation of the entrance of conduit 42 into receiver 40 is such that approximately l0 percent of the total amount of refrigerant supplied from the condenser through conduit I2 on each cycle of operations can collect in the liquid receiver below the level at which it can ilow into evaporator element 4I.

In addition to the evaporating element 4I, a second evaporating element is associated with the liquid receiver 40. A U-shaped conduit 5I! opens into the lowest corner of the liquid receiver 40. This conduit then joins with a slightly inclined conduit 5I passing along and in heat transfer relationship with the lowest portion of liquid receiver 40'. Conduit 5I joins with an upstanding conduit 52 extending around the far end of the liquid receiver 40 and merges into a horizontal conduit 53 lying along and in heat exchange relation with the top of the liquid receiver 40'. Conduit 53 then joins a vertical conduit 54 extending downwardly in spaced rela-- tion to the near end of liquid receiver 4B' and merges into a substantially horizontal conduit 55 which joins the conduit 42 slightly below the elevation at which conduit 5B joins the reservoir*` 40. The conduit system 5I) to 55 inclusive constitutes a second evaporator which is vapor locked for the major portion of the absorbing period of its associated refrigerating system.

At the beginning of an absorbing period of operation of the generator-absorber A, the liquid receiver 40 will be lled with refrigerant liquid to the level indicated by 44. The same liquid level condition will of course prevail within the evaporator system 4i and the evaporator system 5U to 55 inclusive. At the time mentioned above, heat is applied to the generator-absorber A' and shortly thereafter the temperature of the liquid receiver 40' begins to approach the temperature of the cooling medium because warm condensate is discharged thereinto. Simultaneously the temperature in the evaporator system E is reduced very much below this point because cooling of the generator-absorber A has caused the same to ab- Sorb refrigerant and the pressure in its associated refrigerating system has dropped sumciently.

to induce evaporation of liquid at comparatively low temperatures. As a consequence of this temperature pressure relationship, some refrigerant liquid in the conduit 5| quickly vaporizes and flows into conduits 521 53 and 54. It will be noted that the system 52, 53 and 54 is an inverted U-shaped conduit forming a vapor trap and that vapor entrapped therein will push liquid refrigerant downwardly in conduit 54 toward the conduit 42 and out of conduit 5| into the trap conduit 5l. As soon as the liquid is removed from the region in which it is in heat exchange relation with the liquid receiver 40', further evaporation of liquid becomes impossible, and a vapor lock is established by the vapor entrapped in the inverted U-shaped conduit system 52, 53 and 54. The vapor in conduits 52, 53 and 54 balances a liquid column between the liquid level in receiver 40 and the effective liquid level in conduit 5I on one side and equal liquid column between the liquid level in reservoir 40 and the liquid level in conduit 55 on the other side. The trap 50 is preferably extended below the level of conduit 55 to insure that any excess vapor pressure which may develop in the conduit system 50 to 55 will escape through the conduit 55 rather than through conduit 50.

The foregoing .inoperative or vapor locked condition of the conduit system 5U to 55 will continue throughout the major portion of the absorbing period of operation in generator-absorberA during which time the liquid level in the evaporator system E progressively drops from the level indicated in 44 until the liquid level indicated at 56 is reached which is below the connection between conduit 42 and the liquid receiver 40. When this condition is reached, the vapor lock is still effective but further evaporation in the evaporator system E will occur solely from the liquid then contained within the evaporator system 4| and will continue until the liquid level drops suiliciently to vent conduit 55 and hence the vapor lock 52, 53 and 54. When the vapor lock is vented, the liquid trapped in the liquid receiver 40 below the point of connection between the receiver and conduit 42 then flows freely through conduit 50 into conduit 5| where it is in heat exchange with the comparatively hot liquid receiver 40. The liquid in conduit 5| is rapidly vaporized by the hot liquid in receiver 40' to establish a new ternperature pressure equilibrium in the generatorabsorber A. The liquid remaining in evaporator 4| is far below the temperature of the liquid in conduit 5I and no longer evaporates. Evaporation of refrigerant liquid in conduit 5| pre-cools the stored liquid refrigerant in the liquid receiver 40 considerably below the cooling medium temperature. Approximately the last percent of refrigerant to be re-absorbed by the generator- 'absorber A is vaporlzed in heat exchange with liquid receiver 40 to pre-cool the liquid in that receiver. The major portion of this vaporization occurs at temperatures and pressure considerably above those which prevailed in the system before the vapor lock 52, 53 and 54 was vented which increases the absorption rate, and this last remnant of refrigerant is 'evaporated and absorbed in a short period of time.

It will be noted from Figure 3 that all portions 4 of the evaporator system 50 which are above the level at which conduit 55 joins conduit 42 are within the insulated evaporator window closure plates 60 of the insulated cabinet construction Il, therefore such high temperature evaporation as occurred to pre-'cool the liquid in the liquid receiver 40' does not effect the evaporator 4| which remains at a temperature approaching lthe lowest temperature produced during the absorbing period and increases in\ temperature only by such heat as is absorbed from the refrigerating compartment. This last-amount of heat is comparatively small because the absorbing period is quickly brought to an end by the relatively high temperature and pressure evaporation occurring in the conduit 50.

All portions of the evaporator system 4I which are exposed to the objects of refrigeration; that is, which extend outside the insulation 50, are at all times flooded with liquid refrigerant, hence the refrigerant charge in each individual absorption refrigerating system is equal to the amount required to flood the evaporator systems 4|42 up to the level of the juncture of conduits 42 and 55 plus the amount required to saturate the absorbent charge in the generator-absorber A.. Maintaining the main refrigerating evaporator flooded as above described significantly improves the economy of the system for another reason. If the generator-absorber is allowed to absorb all of the liquid in vthe evaporator system it starts the succeeding generating period of operation with a dry evaporator which is usually considerably be- -low the temperature of the cooling medium. Consequently the first refrigerant evolved during the generating period of operation condenses within the refrigerated space and rejects its heat of condensation to the objective of refrigeration and this continues until the portions of the evaporator exposed to the refrigerated space are completely filled with liquid. The present invention effectively prevents this by retaining a flooded evaporator Within the refrigerated space under all conditions of operation.

Only a comparatively insignificant condensation can occur in the evaporator system E; that is, in the liquid receiver 40, however, this receiver is insulated and condensation occurs therein only until its temperature and that of a small amount of liquid initially condensed is raised to the temperature of the cooling medium after which all further condensation occurs in the condenser C.

In considering the evaporating systems E and E each for convenience in illustration and description -has been treated as comprising the vessel 40 as a pure liquid receiver, conduit 42 as a pure liquid supply conduit from liquid receiver 40 to evaporating element 4I1 and conduit 5|) as Stated somewhat differently the evaporator system E, for example, actually comprises a com- `mon liquid supply to evaporators 4| and 5|' so arranged that they are trap separated from each other after the liquid level drops below a prede termined point; that is, each has a connection to the part of the system truly common to the two which forms a liquid trap separating it from the other. Therefore, the low temperature evapn orator 4| and the higher temperature evaporator 5| receive liquid in common from the cony existence of the vapor lock in conduit 52, 53`

and 54 -prevents circulation through the conduit but continued evaporation in the evaporator 4| suiliciently lowers the level in its trap connection to open the vent of the vapor lock and to allow evaporator 5| to go into full operation.

The present invention provides an evaporator system characterized by the provision of two evaporative sections. The first evaporative section is so arranged that any vapor former therein always possesses an untrapped exit to the condenser of the system so that it may return to the generator for re-absorption. The other evaporative section is so arranged that its liquid inlet and vapor outlet are below the highest part thereof so that a vapor trap exists and evaporation cannot occur therein until the liquid level in the evaporator system has lowered to a point which uncovers its vapor outlet to vent the vapor trap or lock.

The present invention further provides a refrigerating system in which approximately 90 percent of the cycling charge of refrigerant is evaporated to produce useful refrigeration at temperatures suiiiciently low to provide substantially continuous effective refrigeration while the remaining percent of the refrigerant which would normally evaporate over an extended period of time and at undesirably high temperatures is evaporated in a short period of time and at still higher temperatures and pressures but under conditions such that it sustains a high temperature refrigeration load which would otherwise be thrust upon refrigerant liquid which could otherwise evaporate at greatly lower temperatures and pressures. Y

In consequence of the foregoing relationship the period of time required, other things being equaLtoevaporate and re-absorb a given quantity of refrigerant is very significantly reduced; the mean temperature of the evaporator is maintained appreciably lower because it is not warmed up by condensation of refrigerant therein at any time and it is not allowed to warm up during the normally long period of time required to reabsorb the last 10 percent of the cycling charge of refrigerant; and the principal refrigeration producing evaporator is relieved of the burden of evaporatively pre-cooling its liquid charge from the temperature of the cooling medium to the refrigeration temperature which it normally maintains in the object of refrigeration. Thus the mean temperature of the evaporator is sig- `nilicantly lower than prior practice and the described in connection with a particular modication thereof, various changes may be madein the details of construction and arrangements of parts without departing from the spiritof the invention or the scope of the appended claims.

I claim:

1. In a refrigerator, a pair of intermittent absorption refrigerating apparatuses each includ- The shortening of the ing a generator-absorber, a condenser and an evaporator structure, control means for successively heating and cooling each of said generatorabsorbers in out-of-phase relation with each other, each of said evaporator structures including a chilling part and a receiver part above said chilling part, said chilling part being connected to the upper part of said receiver and to the lower part of said receiver above the bottom thereof, and conduit means connected to said chilling part below but adjacent to the level of the bottom of said receiver. and extending in heat exchange relation with the other receiver and opening into said receiver at the bottom thereof.

f 2. In a refrigerator, a pair of intermittent absorption refrigerating apparatuses each including a generator-absorber, a condenser and an evaporator structure, control means for successively heating and cooling each of said generatorabsorbers in out-of-phase relation with each other, each of said evaporator structures including a chilling part and areceiver part above said chilling part, said chilling part comprising means forming a path of flow of refrigerant connected to receive refrigerant from said receiver above the bottom thereof and to return refrigerant to said receiver adjacent the top thereof, said receivers being positioned adjacent each other, conduit means connected to each evaporator structure to receive refrigerant from the bottom of the receiver and connected to said evaporator structure below the bottom of said receiver, and the conduit means connected to each receiver including a portion in heat exchange relation with the other receiver and a part positioned above the bottom of the receiver to which it is connected.

3. In a refrigerator, a pair of intermittent absorption refrigerating apparatuses each including a generator-absorber, a condenser and an evaporator structure, control means for successively heating and cooling each of said generatorabsorbers in out-of-phase relation with each other, each of said evaporator structures including a chilling part and a receiver part above said chilling part, said chilling part being connected to the upper part of said receiver and to the lower part off` said receiver above the bottom thereof, and means automatically operative when the liquid level in said receiver drops below the inlet to said chilling part to conduct the remain- -ing refrigerant in said receiver into heat exchange relation with a part of the other refrigerating apparatus system which is normally at an elevated temperature with respect to said chilling part when said automatic means operates.

v4. In a refrigerating system a pair of intermittent absorption refrigerating apparatuses each including an evaporator structure, each evaporator structure including a refrigerating element and a liquid receiver element and a heat transfer element, said refrigerating element having inlet and outlet connections to said receiver element above the bottom therof, said heat transfer element having vertically spaced inlet and outlet connections to said receiver-refrigerating element assembly below the lowest connection between said refrigerating element and said receiver element, and each of said heat transfer elements extending above its highest connection to the refrigerating element-receiver element assembly and having a part in heat exchange relation with the receiver element of the associated refrigerating apparatus.

5. An evaporator structure adapted for use in refrigeration systems of the me in which high f pressure periods of refrigerant condensation and collection are followed bylow pressure periods of refrigerant evaporationA and absorption, said evaporator structure including a first cooling part having a refrigerant vapor outlet at or above the highest point thereof and a second cooling part, said second cooling part having a refrigerant vapor outlet which is below the highest part thereof and is below the maximum liquid level in said evaporator structure whereby said second evaporator is vapor locked until the liquid level insaid evaporating structure is reduced below the vapor outlet thereof.

6. A dual intermittent absorption refrigeration system comprising a pair of intermittent absorption refrigerating apparatuses, each of said apparatuses including an evaporating structure comprising a liquid receiver connected to receive refrigerant liquid from and to discharge refrigerant vapor to other parts of the apparatus, a first chilling evaporator connected to receive refrigerant liquid from said receiver above the lowest part thereof and to return refrigerant vapor to the upper part of said receiver, said first evaporator being so constructed and arranged that refrigerant vapor formed therein has a generally rising untrapped path of flow to said receiver, a second high temperature evaporator connected to receive refrigerant liquid from said receiver below the level at which said first evaporator receives refrigerant liquidtherefrom and having a vapor discharge connection to said rst evaporator below the level of said inlet connection. said second evaporator having parts extending above the level of its inlet and outlet connections to form a refrigerant flow blocking vapor lock.

7. Rei'rigerating apparatus including a pair of intermittent absorption refrigerating systems,

leach of said systems including an evaporating structure, means for operating said systems to generate and evaporate refrigerant successively in out-of-phase relation with each other, said evaporator structures each including a liquid receiver element arranged to have one part below all other parts thereof, the corresponding parts of each liquid receiver being positioned at substantially the same elevation, a chilling element associated with each evaporator structure connected to receive refrigerant from its associated liquid receiver above the lowest part thereof and to discharge refrigerant vapor into the top thereof, said evaporator structures each including a heat transfer evaporator connected to the lowest part of its associated liquid receiver and to a part of said chilling element below said lowest part of the liquid receiver, each of said heat transfer evaporators extending in heat exchange relation with the liquid receiver of the other refrigerating system.

8, In a refrigerator, an insulated cabinet structure having an insulated refrigerating chamber, a pair of intermittent absorption refrigerating apparatuses associated with said cabinet structure each having an evaporator structure including a chilling ,part in heat exchange with the interior of said refrigerating chamber and parts embedded in the insulation of said chamber, control means for operating said refrigerating apparatuses successively on generating and refrigerating phases of operation inout-of-phase relation with each other, said embedded parts of each evaporator structure comprising a liquid receiving and supply structure and a heat trans- Afer structure connected to receive refrigerant liquid from said receiving structure, said chilling part being connected to receive refrigerant liquid from said receiving structure, said receiving element being so constructed and arranged that said chilling part and said heat transfer structure .receive liquid from separate bodies of liquid in said receiving structure when the liquid level therein drops below a predetermined level, said heat transfer structure having a connection to said receiving structure below said liquid level and in the partthereof from which liquid can flow only to said chilling part, and each of said heat transfer structures having parts thereof in heat exchange relation with the receiving structure of the other refrigerating apparatus and parts above the level of its connections to its associated receiving structure. l

9. An evaporator structure for use in dual intermittent absorption refrigerating systems comprising two evaporating assemblies, eachA of said evaporating assemblies comprising a chilling part for refrigerating an object of refrigeration and a heat transfer part and a liquid receiver having a pair of depending parts which connect to a common part at their upper ends, said chilling part and said heat transfer part being each connected to receive refrigerant liquid from indierant vapor discharge connection to the upper part of said liquid receiver, said heat transfer having a vapor discharge connection to the depending part ofisaid liquid receiver which supplies refrigerant liquid to said chilling part, and each of said heat transfer parts being in heat exchange relation with the liquid receiver of the other evaporating assembly. V

10. An evaporator structure for absorption refrigerating apparatus of the type in which periods of refrigerant generation and collection alternate with periods of refrigerant evaporation and absorption comprising, a liquid receiver adapted to receive refrigerant liquid from and to' discharge refrigerant vapor into other parts of the apparatus in operation, a first chilling evaporator connected to receive refrigerant liquid from said receiver above the lowest part thereof and to return refrigerant vapor to the upper part of said receiver, said first evaporator lbeing so constructed and arranged that refrigerant vapor formed therein has a generally rising untrapped path of ilow to said receiver, a second high temperature evaporator connected to receive refrigerant liquid from said receiver below the level at which said first evaporator receives refrigerant liquid therefrom and having a vapor discharge connection to said first evaporator below the level of said inlet connection, said second evaporator having parts extending above the level of its inlet and outlet connections to form a refrigerant flow blocking vapor lock.

l1. Intermittent absorption refrigerating apparatus of the type in which periods of refrigerant generation and condensation alternate with periods of refrigerant evaporation and absorption characterized by an evaporating structure comprising a primary refrigerant collecting and chilling unit assembly, a secondary evaporating unit comprising a refrigerant flow conduit having its end portions connected to said assembly at dierent elevations below the normal maximum liquid level therein and a portion intermediate said end portions extending above said end portions to form a vapor trap to prevent flow of refrigerant through' ma conduit mm1 che liquid level m said assembly drops below one ot aid end pertions.

12; Intermittent absorltion refigertitig appatalus c! the typ in which periods of refrigerant generation and .condensation alternate with periods of refrigerant evaporation and absorption characterized by an evaporating structure cem= prising a primary refrigerant collecting and chill-1 the normal maximum liquid'level thereixrand to 15 2.436.945

12 the upper part o! said secondary evaporatin unit; l Y

evans c. cooNsa REFERENCES crrnn The following references are of I record in the ille of this patent:

I UNITED STATES PATENTS 10 Number Name Date 1,717,173 Slager June 11, 1929 1,718,699 Hapgood June 25, 1929 2,266,964 Kleen Dec. 23. 1941 2,353,715 Af Kleen July 18, 1944 Sutton Mar.` 2, 1948 

